1. Field of the Invention
The present invention relates to a mask used when forming a thin layer on a substrate, and a process of fabricating the mask.
2. Description of the Related Art
Vapor deposition, sputtering, CVD and similar processes are used to form thin layers from various kinds of material. The thin layers are shaped to a certain pattern or configuration, depending upon a purpose of use. If the vapor deposition process is performed with a mask having a fine opening pattern, the vapor deposition process can make a thin layer having a desired pattern.
In this vapor deposition process, the mask is firmly attached to a substrate prior to vapor deposition. The material is then vapor-deposited on the substrate. The opening of the mask decides (controls) the area of vapor deposition so that a desired pattern of thin layer is made on the substrate. The mask is prepared by, for example, electroforming.
The process of making the mask by electroforming will be described. First, a plating substrate with photoresist thereon is prepared, and a fine pattern of resist is made on the substrate by photolithography (i.e., the pattern making process). As a result, some areas are covered with the resist and other areas are not on the substrate. Then, a metal is electro-deposited over the no resist areas on the plating substrate (i.e., the electroforming process). After the electroforming, the deposited metallic layer is removed from the substrate (i.e., the peeling or exfoliating process). The peeled metallic layer becomes the mask which has the opening of the same shape as the resist pattern.
In this manner, the mask has the opening that has a uniform width is prepared. This technique is disclosed in Japanese Patent Kokai No. 10-305670.
The mask is thin so that the mask is easy to bend. Particularly, the mask bends as the mask becomes larger. If the mask bends during the layer forming process, the opening of the mask changes its shape so that the resulting layer does not have a desired pattern.